1. Field of the Invention
The present invention relates to a fabricating method of semiconductor device and more particularly to a fabricating method of a semiconductor device having a fuse.
2. Description of Related Art
For repairing a fault generated in a semiconductor device, there is an art of avoiding the fault by forming a fuse in the semiconductor device preliminarily and cutting the fuse by laser beam. Insulation film having a specific thickness needs to be formed on the fuse in order to prevent malfunction of the fuse. The reason is that if insulation film on a fuse is thicker than insulation film on other fuse, the fuse cannot be cut by laser irradiation having the same intensity.
Conventionally, there has been proposed a method of forming the insulation film having a specific thickness (see Japanese Patent Application Laid-Open (JP-A) No. 11-67054). This conventional method will be described briefly.
First, a fuse region is defined on one main surface of a semiconductor substrate which serves as a base and a fuse is formed in the fuse region on the base.
Next, an insulation film of silicon oxide film is formed on the main surface in which the fuse of the base is formed.
After conductive film of polycrystalline silicon film is formed on the insulation film, a first conductive film pattern is formed on the insulation film by patterning the conductive film. The first conductive film pattern is comprised of a stopper film formed to cover the insulation film in the fuse region and LSI wirings formed in wiring region which is an area with no fuse formed.
Next, a first interlayer insulation film covering the first conductive film pattern is formed on the insulation film and further a second conductive film pattern is formed on the first interlayer insulation film. The second conductive film pattern is constituted of the LSI wirings formed in the wiring region. Next, the second interlayer insulation film for covering the second conductive film pattern is formed on the first interlayer insulation film and further, a third conductive film pattern is formed on the second interlayer insulation film. The second conductive film pattern and the third conductive film pattern are formed of aluminum alloy.
After that, a protective film for covering the third conductive film pattern is formed on the second interlayer insulation film. The protective film is formed of, for example, silicon nitride by CVD method.
After a resist layer is formed on the silicon nitride film by coating with a photo resist, resist pattern having an opening is formed in the resist layer in the fuse region by executing exposure and development to the resist layer.
Next, by dry etching with the resist pattern as a mask, the protective film in the fuse region, the second interlayer insulation film and the first interlayer insulation film are removed in order to form a fuse window. The stopper film is exposed on the bottom of the fuse window.
Next, the stopper film in the fuse region is removed by dry etching. By setting etching selectivity larger than 1 at this time, the stopper film in the fuse region may be removed securely and the insulation film in the fuse region may be left in a specific film thickness. If the stopper film is formed in a size larger than that of the fuse region, a portion of the stopper film is left in a frame-like form.
Currently, a method of forming the first conductive film pattern of the stopper film and the LSI wiring upon fabricating of a semiconductor device having a fuse has been proposed.
However, if the first conductive film pattern is formed of aluminum alloy like the second and third conductive film patterns, the stopper film is formed of aluminum alloy at the same time as when the LSI wiring is formed. Thus, when the stopper film is removed by dry etching, the portion of the stopper film left in a frame-like form within the fuse window is made of aluminum so that the aluminum is exposed within the fuse window. Aluminum corrodes easily and if aluminum corrodes, aluminum hydroxide is generated. There is a problem that aluminum hydroxide generated by this corrosion may make a circuit between cut fuse portions when electrode wiring is etched in a subsequent process, for example, after the fuse is cut out.
As a result of accumulated research by the inventor of this application, a method of forming the stopper film together with a contact plug at the same time as when forming the contact plug for electrically connecting the base with the LSI wiring has been found. According to this method, the first conductive film pattern does not include the stopper film. That is, the stopper film is formed in a layer different from the first conductive film pattern. Therefore, it has been found that even if the first conductive film pattern, that is, the LSI wiring is formed of aluminum alloy, aluminum which corrodes easily, may be blocked from being exposed on a side wall of the fuse window.